Nitrogen Availability as an Aid in the Differentiation of Bacteria in the Coli-Aerogenes Group

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Abstract
The availability of the N of nucleic acid and certain of its degradation products for the Coli-Aerogenes group of bacteria was investigated. The purpose was to secure an approach, other than by carbohydrate studies, to the systematic and physiological relationships of the organisms comprising this group. Previous work on uric acid suggested the possibility of employing the purines for this purpose. The compounds tested included yeast nucleic acid, xanthine, adenine sulfate, uric acid, uracil, allantoin, hydantoin and urea. Over 350 coli-aerogenes strains were used. This collection was considered representative of the Escherichia, Aero-bacter and "intermediate" groups. Xanthine and adenine were attacked by all strains, and consequently had no differential value. The Aerobacter strains utilized the N of all the other compounds; the Escherichia and "intermediate" strains were each able to utilize the N source for Escherichia, but not for "intermediate," strains. Urea was an available N source for "intermediate," but not for Escherichia strains. These data, when correlated with the results of Voges-Proskauer, citrate, H2S, and indol tests, strengthen the evidence for allocating the "intermediate" strains to a separate genus, Citrobacter. About 90% of the "intermediates" gave reactions identical with those of a transfer of the original strain, Citrobacter freundii, the type species of Citrobacter. Studies of N availability provided a means for generic allocation of a number of strains which could not be adequately classified on the basis of carbo-hydrate dissimilation.